Air Pressure: More Powerful Than You Think

March 2017

Air Pressure: More Powerful Than You Think

March 2017

Creating openings in concrete walls presents a very real danger-and it is probably not a danger that comes to the mind of most operators. Most often, operators are thinking about making precise openings. The danger is with air pressure and the weight of the concrete piece that is going to be removed to make the opening. This article looks into the reasons why air pressure is often not considered when making openings, why is should be; and why the proper approach to cutting openings is so important.

One reason why many operators are unsure of the proper and safe approach to cutting openings is outdated or, just plain improper, training on how to secure the piece being cut. In the past, most operators were trained to use wedges, often custom-designed, long, thin tapered wedges to hold the piece being cut. Operators were taught to use the tapered side of the wedges to face the opening so that the spalled concrete would not show in the finished side of the opening.

1: Operators might question the ability for the opening to move

The fact was never questioned that the spall occurs because the maximum compressive strength of the concrete had been exceeded, and this occurs before the full weight of the opening is on the wedge. Nor was it questioned that when the spall occurs, the concrete being cut to make the opening, can shift, pushing the wedge out. Let me reiterate this point. When a spall occurs, the massive concrete piece being cut to make an opening can shift.

3: The only positive method for securing a wall opening is by strapping

Another reason why operators may not consider the danger of air pressure when cutting openings is that they have always been taught that there is no way a 10-inch-thick, or greater, wall will tip because it will jam in the wall before it can fall.

The final reason for an unsafe approach to cutting openings is the "hurry up and get the job done" mentality. Most wall saw operators have made the decision, at least once, to use one wedge or two at the most, to secure a cut piece instead of affixing a strap to temporarily hold an opening in place, to save time. And in most cases, it is pure luck that prevented this piece of concrete being cut from falling out of the opening.